In general, storage device is mainly constituted by a control unit and a data storage medium (for example, a flash memory). The data storage medium includes a plurality of physical blocks, and each physical block includes a plurality of data pages. The control unit is electrically coupled to the data storage medium and configured to perform data write, data read or data erase on the data pages in the physical blocks.
However, the storage device may have data integrity issues caused by frequent data moving, defect in the manufacturing process and aging of data after long-term usage. Therefore, once data write is completed, the control unit of the storage device may use error correcting code (ECC) to perform a correcting operation on the data stored in the storage device. However, the correcting capability of the error correcting code has a limitation (e.g., 60 bits). Therefore, once the data stored in the data pages has an error greater than 60 bits, the stored data may not be corrected by the error correcting code and an error correcting code invalid issue would happen, leading to loss of validity of the data stored in the storage device.